GaWC Research Bulletin 388

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This Research Bulletin has been published in Environment and Planning A, 44 (2), (2012), 255-256.


Please refer to the published version when quoting the paper.


City Networks in the United States: A Comparison of Four Models

X. Liu *, Z. Neal **, B. Derudder ***

The study of intercity networks could help generate a better understanding of our increasingly inter-connected global community. We studied connections between sixty-one major cities in the United States for the year 2010 and employed four major measures of intercity flows: (1) extra-urban connections (Figure A) estimated by a classic gravity model based on the product of pairwise cities’ populations and squared geographic proximity (i.e., with a distance friction factor of two); (2) Internet connectivity (Figure B) between cities measured by the DIMES internet mapper project (Shavitt and Shir 2005); (3) recorded business air-travel flows (Neal 2010) among selected cities (Figure C); and (4) intercity connectivity (Taylor 2001) inferred based on locational strategies of leading advance producer service firms (Figure D).  Two of these networks are observed flows: airline and Internet, whereas the other two are estimated propensity to interact (Derudder and Witlox 2008). The color density and width of lines are proportional to the standardized connection strength (standardized connections more than 10% of the maximum connection were plotted), and we also mapped the ten most central cities in terms of network degree in individual networks. Chicago, Los Angeles, New York, San Francisco, and Washington ranked consistently high in four networks. Network patterns in business air-travel and producer service firms are highly correlated (Pearson correlation coefficient = 0.82) as they both reflect the economic dimension of the intercity network. Internet connectivity, airline network, and firm network have more long-range connections than those being inferred by a gravity model, the only model where San Francisco and Los Angeles enjoy stronger connections with each other than each with New York. Other networks that can be incorporated into this framework include population migration network, leisure air-travel network, modified gravity models (Neal 2010), and cargo transport network.

Figure A: Extra-urban connections

Figure 1

Figure B: Internet connectivity

Figure 1

Figure C: Recorded business air-travel flows

Figure 1

Figure D: Intercity connectivity

Figure 1


Derudder, B., Witlox, F. 2008. Mapping global city networks through airline flows: context, relevance, and problems. Journal of Transport Geography 16, 305-312.

Neal, Z. 2010. Refining the air traffic approach to city networks. Urban Studies 47, 2195-2215

Shavitt, Y., Shir, E. 2005. DIMES - Letting the internet measure itself, available at

Taylor, P. 2001. Specification of the world city network. Geographical Analysis 33, 181-194.



* Xingjian Liu, Department of Geography, University of  Cambridge, Downing Place, Cambridge CB2 3EN, UK, email:

** Zachary Neal, Department of Sociology & Global Urban Studies Program, Michigan State University, 316 Berkey Hall, East Lansing, MI 48824, USA, email:

*** Ben Derudder, Department of Geography, Ghent University, Krijgslaan 281, S8 9000 Gent, Belgium, email:


Edited and posted on the web on 10th October 2011

Note: This Research Bulletin has been published in Environment and Planning A, 44 (2), (2012), 255-256